The linkage between esterase and the retinoblastoma gene on chromosome 13 is being investigated. Various human retinoblastomas from both sporadic and hereditary cases are being propagated intraocularly and subcutaneously in the nude mouse. Esterase D activity and the electrophoretic pattern is being investigated in the primary tumors and those grown in the nude mice. Similarly the chromosome pattern of each tumor is being evaluated using the trypsin-Giemsa banding technique. In addition, blood samples from patients with both hereditary and sporadic retinoblastoma are being evaluated for their esterase D activity. This is a large scale study involving patients throughout the country. Dr. Robert Sparkes at UCLA Medical School is collaborating on this project.